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Exploring Web Image Formats

Module D23h

* About this document... * Audience and Objectives *
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Overview

This is an exercise to familiarize you with different graphic formats used on the Web. We'll make available a couple of images which you will save using variations of the major Web image formats, GIF and JPEG.

We will be using images saved in either Portable Network Graphics (PNG), or Tagged Image File Format (TIFF), a widely-used non-Web format. They are available on:
Website
Local Area Network
http://courses.wccnet.org/computer/mod/d23h_f01.png t:\faculty\krieg\wcc\d23h_f01.tif
http://courses.wccnet.org/computer/mod/d23h_f02.png t:\faculty\krieg\wcc\d23h_f02.tif

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JPEG


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GIF

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What to Turn In

  1. Print this page; fill in the chart and answer the questions. Submit it to your instructor with your name and section number.

    2. JPEG
    People Image
    Text Image
    Quality Level
    Your Opinion (1-10)
    File Size (KB)
    		  
    Quality Level
    Your Opinion (1-10)
    File Size (KB)
    100% Level 12
    		      
    100% Level 12
    		    
    75% Level 9
    		      
    75% Level 9
    		    
    50% Level 6
    		      
    50% Level 6
    		    
    25% Level 3
    		      
    25% Level 3
    		    
    10% Level 1
    		      
    10% Level 1
    		    
    GIF
    People Image
    Text Image
    Quality Level
    Your Opinion (1-10)
    File Size (KB)
    		  
    Quality Level
    Your Opinion (1-10)
    File Size (KB)
    256 Colors
    		      
    256 Colors
    		    
    128 Colors
    		      
    128 Colors
    		    
    16 Colors
    		      
    16 Colors
    		    
    4 Colors
    		      
    4 Colors
    		    
    2 Colors
    		      
    2 Colors
    		    


  2. Answer these questions:
    1. Describe the effect on the people image of 10%/Level 1 JPEG compression.

    2. Describe the effect on the people image of reducing the number of colors to 2.

    3. Describe the effect on the text image of 10%/Level 1 JPEG compression.

    4. Describe the effect on the text image of reducing the number of colors to 2.

    5. Is the quality of the text image the same in a GIF with 256 colors and a GIF with 128 colors? Why or why not?

    6. You are the Webmaster, and must select one people-picture to put on the Website. Which is the smallest people image file that maintains acceptable quality in your opinion.

    7. Again in your role as Webmaster, identify the smallest text image file that maintains acceptable quality in your opinion.


Audience: This is for people who know the basics of image formats for the Web, and want to learn by experimenting exactly what the formats are like.
Objectives: When you successfully complete this lesson, you will be able to...

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About this document...
Module D23h: This document is part of a modular instruction series in Computer and Internet instruction. For more information, see the overview or the list of modules in this series, D: Desktop Publishing and Computer Graphics. This document has been used in the following classes: INP 143/152

Author: Laurence J. Krieg
Institution: Internet Professional Department, Washtenaw Community College
History: Original: 18 May 2000; This revision posted  Monday, 31-Aug-2009 11:47:56 EDT
Copyright © 2000, Laurence J. Krieg.
Instructors: You may point to this file in your Web-based materials.
Students: you may make a copy for your personal use.
All other uses: contact the author, Laurence J. Krieg for permission.
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